Born in North Dakota, Korsmo was raised in Minneapolis after his parents' divorced and his mother remarried. After a trip to Universal Studios in California, he decided he wanted to try his hand at acting. Exceptionally bright, Korsmo was reading on a high school level by age four and was solving college level mathematics by age eight. A dislike for school was partly the driving force that propelled him into show business. After auditioning for local TV commercials, he was spotted by the casting director for "Men Don't Leave" and when the youth tidily summed up his character's dilemma ("My dad's dead, my mom's sick and my life is a mess."), he landed the role. After hosting a segment of the 1992 PBS documentary "The Creative Mind", Korsmo resumed his "normal life", attended high school and enrolled as a physics major at the Massachusetts Institute of Technology (with an eye to joining the US space program). He also kept his hand in acting, occasionally appearing in college productions like "H.M.S. Pinafore". After a seven-year absence, he made a one-shot return to film work in the ensemble comedy "Can't Hardly Wait" (1998), perhaps not ironically playing a science-loving nerd. After graduating from MIT in 2000, Korsmo forsook Hollywood and in 2001 accepted a job at the Environmental Protection Agency in Washington, DC.